IE (Internet Explorer) doesn’t work with user names and passwords in Web site addresses URLs (HTTP/S).
Though, IE versions 3.0 to 6.0 support this.
The following URL syntax may not work in Internet Explorer or in Windows Explorer,
Such URL syntax is used to automatically send username/password to a Web site which requires basic authentication.
A hacker may exploit this nomenclature and make a hyperlink which looks like opening a legal/intended Web site but in reality opens a another, e.g., http://firstname.lastname@example.org doesn’t open http://www.expertsguide.info which you would think should, rather opens http://example.com